The evidence is against it: Polygamous marriages often had other purposes than procreation, one such purpose being to tie faithful families together

Some people have concluded that Helen did have sexual relations with Joseph, which would have been proper considering that they were married with her consent and the consent of her parents. However, historian Todd Compton does not hold this view; he criticized the anti-Mormons Jerald and Sandra Tanner for using his book to argue for sexual relations, and wrote:

The Tanners made great mileage out of Joseph Smith's marriage to his youngest wife, Helen Mar Kimball. However, they failed to mention that I wrote that there is absolutely no evidence that there was any sexuality in the marriage, and I suggest that, following later practice in Utah, there may have been no sexuality. (p. 638) All the evidence points to this marriage as a primarily dynastic marriage.[1]

Thus, polygamous marriages often had other purposes than procreation—one such purpose was likely to tie faithful families together, and this seems to have been a purpose of Joseph's marriage to the daughter of a faithful Apostle.

Critics who assume plural marriage "is all about sex" may be basing their opinion on their own cultural biases and assumptions, rather than upon the actual motives of Church members who participated in the practice.

Evidence from the "Temple Lot" case of non-consummation of Helen Mar Kimball marriage

Researcher Brian Hales has identified a further line of evidence which suggests that Helen's marriage was not consummated. In 1892, the Reorganized Church of Jesus Christ of Latter Day Saints (RLDS, now Community of Christ) brought suit against the Hendrickite, or "Temple Lot" break-off group. They claimed that the Independence, Missouri temple site was rightfully RLDS property, since they were the direct heirs of Joseph Smith's original religious group.

Although not embracing plural marriage themselves, the Temple Lot group was anxious to demonstrate that Joseph Smith had taught plural marriage--for, if this was so, then the RLDS (who denied that Joseph had practiced it, and certainly did not embrace the doctrine) would have difficulty proving that they were the direct successors to the church founded by Joseph.

Among nonpolyandrous wives who were not summoned was Martha McBride who lived in Hooper, Utah (thirty-seven miles to the north). McBride's relationship with Joseph Smith is poorly documented, with no evidence of sexual relations....Also passed by was Salt Lake resident Helen Mar Kimball who had written two books defending the practice of plural marriage. Her sealing to the Prophet ocurred when she was only fourteen and the presence or absence of sexual relations in her plural marriage is debated by historians.

Throughout the lengthy question-and-answer sessions with Malissa Lott, Emily Partridge, and Lucy Walker, the details of their polygamous marriages with Joseph Smith were paramount; the physical aspect of sexuality was a core issue. If [Helen or others] could not testify to such relations, their testimonies as the Prophet's polygamous wives could hurt the Church of Christ (Temple Lot) cause.[3]

Helen's personal account

Helen Mar "took pen and paper in hand before she died to describe vividly her ties as a member of the Latter-day Saint Church during its first two decades of existence in a series of articles published in the Woman's Exponent" in the 1880s.[4]:xi Some of her articles dealt with plural marriage: "Her personal remembrances of those days constitute an important source that, taken together with other first-hand accounts by participants, provides a more complete view of the introduction of one of the most distinctive features of nineteenth-century Mormonism."[4]:xv Helen Mar's writings, an important source of LDS history, were published by BYU's Religious Studies Center in 1997 in a book entitled A Woman's View: Helen Mar Whitney's Reminiscences of Early Church History. The book also includes her 1881 autobiography to her children wherein, concerning her marriage to the Prophet Joseph Smith, she wrote:

I have long since learned to leave all with [God], who knoweth better than ourselves what will make us happy. I am thankful that He has brought me through the furnace of affliction & that He has condesended to show me that the promises made to me the morning that I was sealed to the Prophet of God will not fail & I would not have the chain broken for I have had a view of the principle of eternal salvation & the perfect union which this sealing power will bring to the human family & with the help of our Heavenly Father I am determined to so live that I can claim those promises. [4]:487

Did Helen "confess" to having marital relations with Joseph?

Critics also provide a supposed "confession" from Helen, in which she reportedly said:

I would never have been sealed to Joseph had I known it was anything more than ceremony. I was young, and they deceived me, by saying the salvation of our whole family depended on it.[5]

Compton properly characterizes this source, noting that it is an anti-Mormon work, and calls its extreme language "suspect."[6]

George D. Smith tells his readers only that this is Helen "confiding," while doing nothing to reveal the statement's provenance from a hostile source.[7] Newell and Avery tell us nothing of the nature of this source and call it only a “statement” in the Stanley Ivins Collection;[8] Van Wagoner mirrors G. D. Smith by disingenuously writing that “Helen confided [this information] to a close Nauvoo friend,” without revealing its anti-Mormon origins.[9]

To credit this story at face value, one must also admit that Helen told others in Nauvoo about the marriage (something she repeatedly emphasized she was not to do) and that she told a story at variance with all the others from her pen during a lifetime of staunch defense of plural marriage.[10]

Generally, this statement isn't given a lot of credibility - at least in terms of discussing a sexual relationship. There is no question that Helen resented the sealing to Joseph Smith for a time - because of the sealing, she wasn't allowed to socialize with her friends in some ways (dances, social events with other young singles). This generally reflects the opposite of the argument that is sometimes made: if the marriage had been consummated, then Helen would have understood that she was married, and known why she couldn't participate with her single friends in social activities. Instead it seems implied that she was treated as if she was already married, but without it being clear to her that she was actually married.

Notes

↑Todd M. Compton, Response to Tanners, post to LDS Bookshelf mailing list, no date. It should be mentioned that many reviewers of Compton's work do not agree with all of his conclusions, even though he has collected much useful data.